A battery (e.g., a lithium-ion battery) can have a number of internal state variables (e.g., internal state variable functions). A set of selected internal state variables can be denoted as an internal state. For example, an internal state can include remaining charge, state of health (e.g., capacity fade), remaining energy, and/or maximum peak power, among others. Various internal state variables of a battery can be determined (e.g., estimated) based on measured (e.g., sensed) values associated with the battery. For example, one or more internal state variables can be determined based on measured battery temperature, voltage and/or current (e.g., associated with terminals of the battery).
The determined internal state of a battery may be used in managing the battery. In a hybrid and/or electric vehicle, for instance, a determined internal state of a battery may be used in managing a power train of the vehicle.
Previous approaches to battery monitoring may encounter complications in high power applications, for instance, where slow battery internal electrochemical diffusion phenomena may play a significant role. Further, previous approaches may lack accuracy in some instances due to manufacturing variability of individual battery cell parameters. Accordingly, under previous approaches, batteries may be operated conservatively (e.g., in a reduced range of discharge depth) limiting battery usage potential.